Narrowneck renewal deemed a success

Stu Nettle
Swellnet Analysis

The construction of Palm Beach Artificial Reef on the Gold Coast is due to be completed in October this year. If the project stays on schedule the artificial reef will be completed exactly twenty years after Narrowneck, the first artificial reef to be built on the Coast.

Unlike Palm Beach reef which is made of stone, Narrowneck was constructed using sand-filled geotextile bags. In the intervening years those bags shifted, settled into the sand, or split, often due to anchor strike, hence Gold Coast City Council began remedial work on the reef in late 2017, completing it in mid-2018.

The new work is now a year old, so the results can be assessed, and it can also be viewed against the almost-complete Palm Beach Reef.

Both Narrowneck and Palm Beach reefs are designed primarily to halt erosion - surfing amenity is a secondary consideration. There's only 100 metres of land separating the Nerang River and the ocean so the purpose of Narrowneck reef is to protect the isthmus by mitigating wave energy offshore and allowing a salient (sand build up) to grow on the beach. 

Early observations of Narrowneck report favourable sand build up with a "distinct" and "consistent" salient of between 30 and 50 metres. These observations continued up until 2010. However, Google Earth's historical imagery shows no salient ever appearing shoreward from the reef.

In contrast to early reports, a City spokseperson recently told Swellnet that a salient was never expected to accrete at Narrowneck, rather the sand build up was supposed to occur offshore.

"Previous monitoring and analysis of sand volumes since construction of the artificial reef has shown that the reef promotes an increase of sand volumes in the offshore sand bars, rather than on the upper beach."

The reef renewal at Narrowneck was not intended to change this situation, "but to increase the volume of sand available within the sandbar system."

A year on, and with the City continually monitoring the sand flow, the City considers the project a success.

Anecdotally, the new geotextile bags at Narrowneck have settled with the reef becoming deeper and breaking less often, however those reports don't stack up against testing. "The City has surveyed the Narrowneck artificial reef regularly following the renewal.  The survey data does not show any settlement of the Geotextile Sand Containers."

A similar discrepancy exists in how often the reef is being surfed with locals reporting few sessions, plus Swellnet's own Narrowneck camera showing surfers seldom surf the reef. These observations aren't supported by the City's own monitoring which has shown "a significant increase in the frequency of wave breaking on the reef", adding that "the enhanced influence of the reef on incoming waves, provides additional opportunities for surf amenity on the reef and also on the sand banks inshore and adjacent to the reef structure."

Lastly, despite the Palm Beach artificial reef using quarried stone, the City has no plans to switch materials at Narrowneck. All future renewal work will "likely to be undertaken using Geotextile Sand Containers consistent with the reef’s design."

Comments

warddy's picture
warddy's picture
warddy commented Monday, 19 Aug 2019 at 12:45pm

Absolute waste of money ...
When will these clowns realise just drop some rocks in a triangular shape and whamo pick a peak and dissipate the sand surge at the same time plus create a fisherie .

Fish Face's picture
Fish Face's picture
Fish Face commented Wednesday, 21 Aug 2019 at 10:07am

Because that would be too easy and wouldn't justify the jobs of the "experts" who created this abomination.

frog's picture
frog's picture
frog commented Monday, 19 Aug 2019 at 5:47pm

My observations in the wild suggest that sand accretion inside an offshore bombie or island will occur if a clear cut bend in the swell occurs on either side of the obstruction. The simple sign of this occurring is:

Do inside wedge type a-frames occur through bent swells crossing each other?

If so, sand will build up causing beach widening due to:
1. the point in the lee of the island / bombie being a lower energy point due to broken swell more often occurring further out from the shoreline at this point allowing more energy to dissipate and so sand to settle more easily inshore.
2. a mini longshore drift effect that gets set up on either side of the lee point by the angled waves that directs sand towards a broad focal point on the beach.

Bending swell requires, at minimum, the waves to strongly feel bottom for at least a multiple of 2 times the wavelength to slow the swell down along the shallower reef or island edge. The Queenscliff bombora is too deep to have this effect in most smaller swells to any greater extent - hence the fairly straight Manly beach profile. Thirteenth beach, however has a much shallower and larger scale bombie well out to sea that bends swells a lot creating the convex beach shape there.

Narrowneck does not look like it has enough sustained shallowness to do this and I have never seen a photo showing much of a wedge type peak inside the reef.

In major swells it would have some protecting effect immediately inside the reef but the beach widening is minimal.

Frogg

the-spleen_2's picture
the-spleen_2's picture
the-spleen_2 commented Monday, 19 Aug 2019 at 2:33pm

I used to surf up that end a lot, including Naz, and never noticed a salient. A friend of a friend was in the original Griffith pitch and "beach widening" was the core of the project so it's funny to see how the idea has changed over time.

Fish Face's picture
Fish Face's picture
Fish Face commented Wednesday, 21 Aug 2019 at 10:13am

Yeah classic case of changing the goal posts when you don't get the results you wanted!

truebluebasher's picture
truebluebasher's picture
truebluebasher commented Monday, 19 Aug 2019 at 5:29pm

tbb will companion a confronting local version of post Narrowneck Reef events

Feb/2019 'Cyclone Oma' video(Worst erosion at Narrowneck)+worst in 40 yrs!
https://www.dailymail.co.uk/news/article-6740523/Cyclone-Oma-takes-big-b...

https://cdn.newsapi.com.au/image/v1/436adc09244309a71e7cf73399014e43?wid...

https://cdn.newsapi.com.au/image/v1/d2bb86520f1b4e56976d111259313129?wid...

1st/June/2019 GCCC works promote massive scarping & Beach-long closed sections
@ Slydefest. Dune erosion was so bad tbb guided LG's 4wd down blinded chute.

July big winter seas shuffle Narrowneck Reef sandbags as evidenced by Surf cam.
29/July PB Reef rep informs tbb that Machiavelli will sort Narrowneck Reef kerfuffle.

Big Winter swell/s 'News herald Narrowneck as worst eroded GC beach.'

My'GC showcases proposed Narrowneck SLS'Clubhouse site /GCCC beaches update.
http://www.mygc.com.au/mayor-happy-with-progress-being-made-to-repair-go...
+
Collection of grainy (contraband) GCB Photos of Mid Winter Narrowneck erosion...
https://lh3.googleusercontent.com/z0ObW8gEdjNreLsjK51fldWUL7TV0Po4XR5I6j...

https://lh3.googleusercontent.com/swSLyaKqAxIumDO1IoxIDCZpREvc5hnydiQP50...

Mayor did also say! "It would've been worse without the Reef."(Shocking revelation!)

tbb has painted a fair picture of 2019 events so crew can judge Reef for themselves.
Local's call! Undoubtedly Narrowneck presented healthier before reef & heavy seas.

Crew salutes #1 Swellnet for dedicated Narrowneck Reef reporting & comments.

frog's picture
frog's picture
frog commented Monday, 19 Aug 2019 at 5:56pm

No-one escapes the tbb inquisition

Those photos of Oma erosion with stormy seas behind it just show how tiny the narrowneck reef is in the scheme of things - no more than a speed bump in Oma's path.

Frogg

bukz's picture
bukz's picture
bukz commented Monday, 19 Aug 2019 at 6:57pm

Just look at that job, they just displicently threw sand bags on deep water hoping for quality waves and avoiding erosion?

That thing should be built o the low tide mark and have a shape that can trap sand and create shallow banks where it matters. Close to shore.

bluediamond's picture
bluediamond's picture
bluediamond commented Monday, 19 Aug 2019 at 10:51pm

The band aid coast.

yocal's picture
yocal's picture
yocal commented Tuesday, 20 Aug 2019 at 4:00am

I reckon it goes OK. Not epic but OK.

Same as the nearest true reefbreak to Narrowneck, the wave quality deteriorates when the offshore storm bar is dominant, but I've been out and seen a bunch of waves that look fun and have definitely noticed more peaks inshore at high tide.

Go deeper Taylor, go deeper!

Spuddups's picture
Spuddups's picture
Spuddups commented Tuesday, 20 Aug 2019 at 5:20am

"I reckon it goes OK. Not epic but OK."

https://www.youtube.com/watch?v=Mg5HOnq7zD0

neil.jeffries's picture
neil.jeffries's picture
neil.jeffries commented Tuesday, 20 Aug 2019 at 11:33am

When the project was originally proposed there was an information centre set up at the south car park Narrowneck. There was written and visual plans as to what the reef was to achieve. The powers that be have stated recently that the reef was only intended to change the flow and depositing of sand around the reef, which in turn would then have an effect to both the north and south of the reef and was not designed to create new wave breaks .On the original plan l remember that the reef was to be around 600 mts to the outer edge of the reef and a designated paddle out channel through the middle, with wings extending off either side to create a left and right breaking wave .This was supposed to create a safe swimming area or lagoon area inside the reef. It would be interesting to hear what the original marine engineers had to say as to whether my memories are correct on this matter. the information l was told was that those engineers walked off the job because the original plan was not being followed. l can stand corrected on this or any other point but that's how l remember this project being implemented

lostdoggy's picture
lostdoggy's picture
lostdoggy commented Tuesday, 20 Aug 2019 at 12:07pm

A bit of info in here on the original design and changes made. There was mention of a paddle channel,

https://pdfs.semanticscholar.org/c119/9156bf6eed970de4555c7fad445d63bcbc...

This claim seems a bit dubious to me though.

“GPS data shows that recorded rides average 150 to 200 m, but have reached up to 260 to 270 m. Similarly, recorded ride times have reached up to 60 seconds.“

Average rides of over 150m? Got to be kidding.

A 60 second ride? What were these guys riding? 12 foot gliders?

Where do they get an average from anyway? Are they getting GPS data from all surfers?

truebluebasher's picture
truebluebasher's picture
truebluebasher commented Tuesday, 20 Aug 2019 at 12:17pm

neil.jeffries' ( i ) stand ...good call, tbb pulled up here also.
https://upload.wikimedia.org/wikipedia/commons/b/b0/Mega_sand_container.jpg

GCCC CEO yocal earns $600k/yr *more than PM, to stuff words down Mayor's mouth.

GC Mayor Spuddups : "$100m Narrowneck Reef 1/40 yr fail smashes 1/100 yr fail."

Ye Olde Goldie Tourism Promo!

Narrowneck Reef Costings (Not included)
Pre 2017 Seawall/s -Rock+Timber +Path works
Beach Sifting + Car Parking
Patrols + Security + Reviews (Note Ocean Temp is recorded @ volatile Narrowneck)
Narrowneck slsc site works + Rainbow Dredging
Beach Erosion repair is a never-ending expense @ Narrowneck
Narrowneck is Qld's most heavily eroded beach.(Cost = A fortune)...not included

Narrowneck Reef/Beach calculated in 2017 AUD ( Cost includes handling & shipping )

1999-2000 ($89.5m) Reef Design + Original - 392 bags
2001-2006 ($=1.7m) Reef - 4 x Top Ups - 58 bags
2017-2018 ($=2.5m) Reef - 2 x Top Ups - 84 bags
2017-2018 ($=4.2m) A Line Rock Seawall - 600m > North
2018-2019 ($=0.9m) A Line Rock Seawall - 200m > South
2017-2019 ($=1.8m) Oceanway Path +Toilet Block renewal
1999-2017 ($100.6m) Narrowneck Reef Total Cost in 2017 AUD)

{ Shoebox }
http://news.cityofgoldcoast.com.au/media-releases/protecting-narrowneck-...
lostdoggy links to original Reef cost (converted to 2017 $)

2017 Palm Beach Reef ($2m) Phase 1 (470,000m3) Reef podium/PB contouring
2019 Palm Beach Reef ($18.2m) Phase 2 (Boulder Reef)
2019 Palm Beach Reef ($ ?) Phases 3-4(11th Ave Sand Cape+4th Ave Sand Bommie)
2017-2019..... PB Reef ($20m) approx

neil.jeffries's picture
neil.jeffries's picture
neil.jeffries commented Tuesday, 20 Aug 2019 at 6:26pm

Have just had a look on the city councils web site showing a photo thats supposedly the artificial reef, looks more like Rainbow Bay to me. Just after they finished the reef l went for a dive on the reef to get an idea on what they'd done . The bags were, according to what l'd read at the information centre to be placed parralelll to the terrace what l found was that the bags were all over the place quite a number were running east west instead of Nth Sth in this day and age with Global positioning sats they should have been able to put those bags in a very precise position, which makes me think that perhaps the job wasn't done properly in the first place. Perhaps another instance of our council going for the cheap option and not doing their homework. CAN SOMEBODY COME UP WITH THE ORIGINAL PLAN . This is our money they're spending. For my part l don't think there listening to the right people I've been surfing for 59 years and was in the fishing industry for 10 years , there must many more people like myself with a wealth of knowledge here on the coast that could have an input into this topic . If these reefs are being designed on computer models then maybe we should be looking at local knowledge from long time surfers and fisherman that have seen what was been happening over the last 40 or so yeas because in the 35 years i've lived on the coast a lot of my hard earned cash has been pumped onto our beaches only to end up travelling Nth to replenish the sunshine coast. Last bitch ...if the council is saying that the beaches are being stabilized ..why is there a 25 ft bank in the Narrowneck terrace and up untill the last couple of weeks there has been no decent banks there for 12 months or more END OF RANT ALOHA ALL

truebluebasher's picture
truebluebasher's picture
truebluebasher commented Tuesday, 20 Aug 2019 at 10:11pm

neil.jeffries talk of a lagoon...not gonna rule out a lagoon due to the timeline of Reef.

1980-90's (GCCC Surf Sandbags & Sandbag Lagoons)

1985 GCCC Miles Street North Kirra Sausage Groyne 120mL x 12mW x 5mH
1.2m diameter Geo Textile Tubes stacked in a Pyramid style.
Cost was said to be cheaper than Rock Groyne of similar build.
Vandals cut the bags open,despite repairs the front edge fouled + odd repairs failed.
These 2 links detail the Kirra Sausage Groyne

https://books.google.com.au/books?id=kUuz-gPDGmQC&pg=PA257&lpg=PA257&dq=...

https://www.researchgate.net/publication/297089014_Performance_of_Sand_F...

Broadwater swim enclosure / Harley Park Lagoon were big news alongside Surf Reef.
Late 1990's Harley Park Lagoon laid out longer thin sausage style geo textile bags.
These bags were then sand sprayed to resemble natural sand weir. (Click on photo)
https://digitalbank.goldcoast.qld.gov.au/vital/access/manager/Repository...
Reef design may well have featured a Lagoon as they were standard fare in 1999

Again, you're not imagining the Reef sand bag placing being at odds.
2004 (6 bags) were Right angled (N< >S) to bridge the (E< >W) Reef Alignments.
Link to swellnet- Watch- Aerial view of Palm Beach Reef site re: tbb 25/July/2019
https://www.swellnet.com/news/swellnet-dispatch/2019/07/22/watch-aerial-...

Fish Face's picture
Fish Face's picture
Fish Face commented Wednesday, 21 Aug 2019 at 10:26am

I really don't understand why the City is committed to keep using those bags at Narrowneck rather than switching to rocks. They don't work. I've been spearfishing there for years and they are just a mess - all busted open and waving around like man made seaweed.

thermalben's picture
thermalben's picture
thermalben commented Friday, 23 Aug 2019 at 7:52am

First wave I've seen break at the reef in a long time.

simba's picture
simba's picture
simba commented Friday, 23 Aug 2019 at 7:58am

its a hoax

simba

truebluebasher's picture
truebluebasher's picture
truebluebasher commented Friday, 23 Aug 2019 at 10:05am

Gold Coast ratepayers salute thermalben's observation & insightful timing...
Reefer Madness as Stu teed off on Palm Beach Reef...{swellnet #1 Surf forecasters}

swellnet stop clock reads [7:37] Low tide @ 6:53 =[ 0.3m] recording is ultra valuable.
This bookends Stu's observation of half built Palm Beach Reef firing up as it did!
PB Reef first broke waves on 16/6/2019 Low tide =[0.21m] also on new Sth swell.
For the record: Strong southerly front + overcast bringing rain both times.

Turn of the tide brings in new Southerly Swell & all things considered should fire up...
Wave of the Day ~~~~^~~~~/(`~~~~/(C`...[ Ben )

Sheepdog's picture
Sheepdog's picture
Sheepdog commented Friday, 23 Aug 2019 at 5:47pm

Now maybe throw a reef/s out in front of the north end of Bribie Island, where the erosion has nearly broken through. Clown town surfers would be stoked to have a couple more options during big east swells. Just a quick paddle across happy valley

https://www.abc.net.au/local/photos/2013/11/15/3892074.htm

Sheepdog

thermalben's picture
thermalben's picture
thermalben commented Saturday, 24 Aug 2019 at 7:10am

Sequence of a set wave this morning.

Notice (1) the first wave (first image) missed the reef and broken on the inside (you can see the resulting reflective wave in the vicinity of the reef), (2) the second wave (second image) capped on the reef but didn't break, though did half-heartedly break further on the inside to the north (third image), however the third one broke (fourth image onwards) and peeled reasonably well (though it's pretty fat), and offered a crumbly close out section at the end.

Most sets are pushing over the reef and not breaking at all. Low tide of 0.31m is in about half an hour's time. Surf size is around the 4ft mark, wave buoy just offshore still has Hsig of ~1.4m with Tp of 13-14 seconds, due E/SE (though regional swell direction is S/SE).






truebluebasher's picture
truebluebasher's picture
truebluebasher commented Saturday, 24 Aug 2019 at 12:30pm

Narrowneck Reef Film Festival to Compliment Feature Article.

(Film 1) Highlights Unique Reef Construction Techniques...(Thinking mans choice)
https://www.youtube.com/watch?v=-dv4n1YoLsY
Menu
[Part 1]
[0:00] Compulsory Surfie Montage may contain...
Wave Sound / Sunrise/Hippy Guitar cue Surfer's board & Leggie.
[0:12] Titles "Narrowneck Reef" (Northern Gold Coast Beach Protection Strategy).
[0:20] Intro Reef Description.
[0:26] Main Road History
[0:40] Tender +Surf Surveyors
[0:50] Beach Nourishment + Rainbow Dredging & Seaway Footage

Halt! [STOP] the Surf Flick...now back up a bit & (PAUSE)Right about there. Wow!
[0:55] Seaway Secret Spot Vid... / / / A frame \ \ \
Mayor's {Stop Work Order}..."Tools Down - Surfs Up!"

Grumpy Boss says back to work
[1:00] Control Point Mechanisms
[1:15] Apprentice Grom goes back for more sultanas cops the sack-back on the Dole.
[1:21] Why a Reef (Includes beach / surf footage)
[1:40] Safer Beach Stability for Safer Lifeguard Patrols

[1:50] Intermission (Goldie Beach Montage plays out with Hipster Guitar Hook)

[Part 2]
[1:56] OZ Dredging industry developed on Gold Coast
[1:58] Sand Bag Reef Contractors
[2:05] Split Hull Hopper Barge
[2:08](L > R) Myr' Lex Bell (NN reef).Cr Daphne McDonald (PB Reef).Cr Gary Baildon.
[2:10] Info Stand (Open Day) Esplanade @ Sth Narrowneck.
[2:14]*Dredge surfing - between the Sets
[2:17] GPS Commodore - Bag Placement
[2:19]*Wave Spotters (Check when next Wave Breaks over the Stern)
[2:27] Tiers..Dredging / Filling / Layering
[2:33] Bag Drop
[2:39] Fly over
[2:40] Monitoring
[2:53] Geo Textile Reef Life. (Under Water Reef cam)
[3:30] Aerial Wrap includes Data / Monitoring-Web Cams...(Mission Complete)

[3:52] Happy Ending (Warning) may contain....
GC Surfboard rider meditating to Hippy Guitar with Rolling Wave @ Sunrise or set.

(Film 2) Down the Hatch of Narrowneck Reef ( Noisy Bubbles! Cue own Soundtrack)
https://www.youtube.com/watch?v=crzsn6h_5mk

(Film 3 part 1)(2003) Mutant years showing the lefthander
https://www.youtube.com/watch?v=LWoL87P12dc
(Film 3 part 2) (2003) The Walled up Right into the backbreak
https://www.youtube.com/watch?v=ruZsqqYGIf0

(Film 4)(2006) Honey Moon Phase or Golden Years (Massive Crowds)
https://www.youtube.com/watch?v=eXDLyoMnhI4
Big days lit up like a sporting Arena seen from Miles away (Big long rides)
Anchored Tinnies pitching overhead in massive pits often resulted in fisticuffs.
Whole Line-Up 'd shout ..."Move yer fuckin Boat"...never ended well! (tbb reef era)

(Film 5)(2010) Barrel Shape backed down by 2013.(Tip! Turn down Volume)
https://www.youtube.com/watch?v=ixVv0_Ty1-c

(Film 6)(2012) The Left ...Excellent example of Narrowneck Reef Left shoulder hopper.
https://www.youtube.com/watch?v=zCJz_4wpOKY

(Film 7 Part 1) (2016 ECL) Sunday Muddy Sunday-The Mud Bath!
https://www.youtube.com/watch?v=lYxQMHtgr-A
(Film 7 Part 2) (2016 ECL) Sunday Muddy Sunday -The Wash-Up!
https://www.youtube.com/watch?v=V6UxtSzN70U

(Live Cam)Thanx Swellnet.
https://www.swellnet.com/surfcams/narrowneck

truebluebasher's picture
truebluebasher's picture
truebluebasher commented Tuesday, 17 Sep 2019 at 1:09am

16th Sept 2019 (9 Gold Coast News)
Narrowneck & Main Beach crews are concerned over large scale scarping.
Images of vert drops with strewn vegetation resemble that of small cyclonic erosion.

Notes: Outer right bank to north of Reef & one inside right to south push through.
Both said left-banks merge into back break. The erosion centres both banks.

Theory!
Top up- stacked Book ends, trapping the tide to act like a weir, welling up inside fuel.
Washing machine whirlpools until the tide drops to release the reef's boiling brew.
Same fault rolls out citywide & GCCC fails to see obvious bommie erosion design flaw.

tbb reckons part of the answer could be blowing in the wind...(next time!)